Interlocks between a transmit bar and a monitor button are known in the prior art, but are complex and subject to maintenance problems. A prior art presently known to me comprises a coiled spring having one end anchored to the microphone base and an opposite end in the form of a rectilinear leg which extends tangentially from the coil and blocks downward movement of the transmit bar. The leg is normally positioned between a stationary bracket and the transmit bar to prevent the latter from being depressed. When the monitor button is depressed, a cam thereon shifts the spring leg about the axis of the spring and clear of blocking position with respect to the transmit bar. Any bend in, or flexing of, the spring leg may defeat its locking operation. Further, the coil and cooperating parts are more difficult to assemble, and thus maintenance and repair are quite a problem, especially since all operating parts, switches and the like are carried by a cover housing and connections are not readily accessible.
In contrast, my invention utilizes a simple lever which is pivoted to the base of the microphone. Also carried by the base, and readily accessible when the cover housing is removed, are the required switches and the pivotal mounting for the transmit bar and monitor button. Further, the monitor button is locked in a simple manner in my invention, as opposed to a latching spring required in the prior art device.